Overview - ISO 7605:2025 (Underwater acoustics - Measurement of underwater ambient sound)
ISO 7605:2025 defines requirements and recommendations for measuring and reporting underwater ambient sound as characterized by sound pressure and derived quantities. The standard covers equipment performance, hydrophone calibration and deployment, digital data acquisition and data processing for recordings of duration one day or longer. It specifies five data-processing stages - raw digital acquisition data, sound pressure time series, sound pressure level time series, sound pressure spectra, and their statistics - and explicitly excludes measurement of particle motion.
Key topics and technical requirements
- Instrumentation and performance: Recommended minimum performance specifications and key characteristics for hydrophones, analogue acquisition, sampling systems and complete acquisition chains.
- Calibration: Calibration requirements, in‑situ checks and calibration regimens to ensure traceable sound pressure measurements.
- Deployment: Guidance on deployment options and mitigation of parasitic signals such as flow noise, cable strum, mechanical and electrical noise, and biofouling; includes bottom‑mounted and cabled systems and recovery considerations.
- Data acquisition & formats: Digital acquisition, file formats, scaling factors and assumptions for waveform data.
- Data processing stages: Clear workflow from raw data to derived descriptors - time series, sound pressure levels (SPL), power spectral density (PSD), decidecade/millidecade bands, narrowband spectra and statistical summaries.
- Advanced processing & statistics: Percentile levels, hybrid millidecade processing, uncertainty considerations and time‑bandwidth effects.
- Reporting & metadata: Mandatory metadata (equipment IDs, calibration, timestamps, geospatial coordinates, navigation track, meteorological/oceanographic context), averaging times, analysis windows, frequency bands and dataset stewardship.
Practical applications and who uses it
ISO 7605 is intended for professionals involved in underwater noise monitoring and acoustic environmental assessment, including:
- Marine acoustics researchers and laboratories
- Environmental consultants and regulators assessing compliance and baseline studies
- Offshore industry (oil & gas, wind farms) and shipping sectors for noise impact assessments
- Conservation organizations monitoring effects on marine mammals and fauna
- Ocean observatory and passive acoustic monitoring providers
Typical applications: long‑term ambient noise baselines, shipping noise studies, offshore construction monitoring, marine habitat assessments, and research into soundscape ecology.
Related standards
ISO 7605 complements other international standards and guidance on underwater acoustics, instrumentation calibration and environmental noise monitoring. Users should pair ISO 7605 with applicable ISO/IEC guidance for instrumentation, data formats and laboratory calibration to ensure comprehensive, traceable acoustic measurements.
Keywords: ISO 7605, underwater acoustics, ambient sound measurement, sound pressure level, hydrophone calibration, underwater noise monitoring, power spectral density, deployment guidance.
